DEMs and Urban Flood Modelling Dual-drainage concept (1D/1D and 1D/2D) Sewer system (manholes and pipes) Overland system (depressions and flow paths)
Overland system 1D overland flow modelling Overland system consists of nodes (ponds) and links (flow paths), generated using DEM. 2D overland flow modelling Surface divided into small elements (squares or irregular triangles), the flow equations (St. Venant) are based on terrain characteristics derived from the DEM.
Network simplification strategies Pruning: <10m; <300mm Merging: similar hydraulic capacity - difference in dimension of consecutive links <100mm First strategy – Simplifications are applied to the sewer network and the overland network simultaneously (1D/1D model) Second strategy – Simplifications are applied first to the sewer network and then to the 1D/1D model network, i.e. including the overland flow network